To achieve an accurate alignment between two machines such as an electric motor directly coupled to a driven machine requires movement of the electric motor to within 0.001" or closer in the vertical and horizontal planes.
When the position of the motor relative to its driven machine are established, the alignment in the vertical plane is achieved by raising the motor to add or subtract metal shims. The raising or lifting of the motor is not critical, as its correct alignment position is established by the shims. Lowering the motor on to the shims achieves accurate alignment in the vertical plane.
In the horizontal plane however, any movement is critical. Heretofore the most common method used to achieve horizontal alignment was by using a heavy hammer or heavy metal `bumping` bar to tap the motor in the direction required. As little control can be exercised over the force of the blow, or the sliding friction of the motor, this method results in a too little--too much trial and error movement, requiring many moves before an alignment or compromise position is reached, involving much time and patience on the part of the mechanical doing the alignment.
In certain circumstances when the construction of the machine base is suitable, another method of horizontal movement may be used. This involves fabricating metal lugs, drilled and tapped to accept a jackbolt, and welding these lugs adjacent to each foot of the motor. The jackbolt is screwed to contact the edge of the foot and push the motor in the direction required.
The jackbolt threads in contact with the foot distort as the jackbolt is turned, and in some cases the jackbolt will bend, making removal difficult if not impossible. Left in position the lugs and jackbolts are subject to deterioration making them unusable the next time motor movement is required, as a result they have to be removed and replaced. Lugs and jackbolts have to be made and fitted to each piece of equipment that is suitable for this method of movement. This method is costly and time consuming.